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Drop test simulation of a mobile device
With support from CADFEM, Motorola simulated a comprehensive case and electronics drop test for a mobile device based on Ansys FEM and LS-DYNA calculations.

Drop test simulation of electronic devices

Sector: Consumer goods/durable goods, Electrical engineering/electronicsSpecialist field: Structural mechanics

The drop test is the toughest test for the structural integrity of handheld electronic device structures. Typical defects occur, such as the loss of connection between the parts of the plastic cover or cracks, as well as damage to the electronic components on the circuit board and the failure of solder joints between electronic components and the circuit board.

Summary

Task

A simulation is designed to analyze the effects of a fall quickly and comprehensively on a mobile device. Both the behavior of the housing as well as that of the electronics are to be examined.

Solution

Performing a drop test scenario using simulation and FEM calculations is widely accepted and established in the industry. LS-DYNA and Ansys are proven software packages for simulations in this area.

Customer benefits

CADFEM combined explicit and implicit calculation methods in the simulation. This coupling allows you to combine the advantages of explicit and implicit time integration without having to worry about non-convergence or time steps that are too small. Short simulation times and highly detailed results for further evaluation of the structure are therefore possible.

Project Details

Task

The drop test is the toughest test for the structural integrity of handheld electronic device structures. In this process, typical defects occur, such as:

  • the loss of the connection between the parts of the plastic cover
  • cracks inside the plastic cover
  • damage to electronic components on the printed circuit board
  • failure of solder joints between electronic components and the printed circuit board

Performing a drop test scenario using simulation and FEM calculations is widely accepted and established in the industry. LS-DYNA and Ansys are proven software packages for simulations in this area. Typically, different mathematical algorithms are implemented in these codes for the transient solution of an impact load. Generally, highly transient analyses are efficiently solved by explicit codes like LS-DYNA. However, due to the time step criterion and the associated mesh size requirements for explicit methods, further Ansys FEM calculations are required as implicit code to resolve local stress fields.


Customer Benefit

CADFEM combined explicit and implicit calculation methods in the simulation. This coupling allows you to combine the advantages of explicit and implicit time integration without having to worry about non-convergence or time steps that are too small. Short simulation times and highly detailed results for further evaluation of the structure are therefore possible.


Solution

The previously mentioned typical failure types can be divided into different scales:

  • the macro-scale considering global structural parts and
  • the micro-scale with possible failure mechanisms within the electronic parts.

Due to the different boundary conditions for the various integration methods, using a purely explicit or a purely implicit solver to calculate the structural response for both the global model and the highly detailed electronic components is not practical. The solution to this contradiction is a combination of the explicit method for simulating the overall structure with a very coarse description of the critical parts and the implicit method for simulating a partial model with the specific components. In this case, the load time histories of the global analysis are simply used as a boundary condition for the partial model.

Images: © motorola


Head of Business Development

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